Background
Spiral grain angle (SGA) is an important factor affecting the distortion and utilisation of solid timber. Little research has investigated how SGA varies at a fine scale within trees and whether this fine-scale three-dimensional variation is similar between genotypes. The objectives of this research were to (i) characterise three-dimensional variation in SGA within stems and clones, and (ii) understand how intra-stem variation in SGA varies between genotypes.
Methods
Detailed measurements of SGA were taken from 12 radiata pine (Pinus radiata D. Don) clones. Analyses were undertaken to characterise variation in three dimensions and determine if this variation significantly differed between genotypes.
Results
Spiral grain varied significantly with distance from the pith, showing a sharp initial increase with distance from the pith, followed by a gradual decline. Values of SGA increased significantly with height up the stem, reaching a maximum at ca. 5 m. Circumferential variation in SGA showed no significant trend. There was significant variation in mean SGA between clones; however, the within tree patterns in SGA did not significantly vary between clones.
Conclusion
If further research confirms the uniformity of within tree patterns in SGA between clones this may greatly simplify efforts to model three-dimensional variation in SGA.